A processing apparatus of a stack is known (Patent Document 1). The stack includes two substrates attached to each other with a gap provided between their end portions. The processing apparatus includes a fixing mechanism for fixing part of the stack, a plurality of suction jigs that fix an outer peripheral edge of one of the substrates of the stack, and a wedge-shaped jig that is inserted into a corner of the stack. Each of the plurality of suction jigs includes a mechanism that allows the suction jig to move separately in a vertical direction and a horizontal direction. The processing apparatus of a stack also includes a sensor for sensing a position of a gap provided between the end portions in the stack. A tip of the wedge-shaped jig moves along a chamfer formed on an end surface of the stack, and the wedge-shaped jig is inserted into the gap between the end portions in the stack.
Unfortunately, a liquid crystal display device including a substrate formed of a general plastic material having a large retardation is known to have a narrow viewing angle. An optical compensation method for improving a viewing angle of a liquid crystal display device and a method for manufacturing such a liquid crystal display device are known (Non-Patent Document 1).